Well casing



Nov. 30, 1943. E. l. CARTER WELL CASING Filed March 3, 1941 2 Sheets-Sheet l INVENTOR 50114425 Z.- C'i'f 2 Sheets-Sheet 2 INVENTOR pu/720 L, meme. BY

z md -TT'OZHEYS qov. 30, 1943. E. L CARTER WELL CASING Filed March 3, 1941 .g. W53@ a 2 M 7 7 2. ww 20d 3 Patented Nov. 30, 1943 UNITED STATES PATENT OFFICE WELL CASING Edward L. Carter, New York, N. Y., assigner to Y The Dow Chemical Company, Midland, Mich.,

a corporation of Michigan Application March 3, 1941, Serial No. 381,523

4 Claims.

The' invention relates to a method and apparatus for completing deep wells, such as oil, gas, brine, or water wells. l

It is conventional practice in completing many wells to line the well bore adjacent the producing formation with a metal screen or perforate metal liner in order to prevent the well bore adjacent the producing formation from caving and to prevent the infiltration of sand particles into the well where they would act to abrade and ruin the pump provided to raise the oil or other mineral fluid to the surface. However, screens and liners are quite easily damaged so that it is diflicult to place themin the well bore at the desired location without damaging them, in some instances to the extent that they may be unfit for use. In addition, as the screen is lowered into the well the slots or -perforations provided to allow the entrance of fluid into the well bore while excluding sand or the like may, and often do, become clogged with mud deposited on the face of the formation during the drilling operation so that the desired mineral fluid is prevented from entering the well.

If an attempt is made to wash the mud vfrom the slotted liner as well as the face of the formation in order to facilitate the ow of oil into the well, generally unsatisfactory results are obtained because the water or other fluid being used as a washing liquid flows out of the perforate liner at all points and causes the mudon the face of the formation to slough oi and fill the annular space between the liner and the ywell bore, instead of passing out of thebottom of the liner and circulating up past the mud in such a manner as to create a washing action on the face of the formation and thus carryl the loosened mud from the well.

A further problem is presented in those instances where the well passes through several producing zones prior to its being drilled into the zone from which it is desired to obtain production. In vsuch cases it is desirable to'provide a suitable screen or perforate liner adjacent each of these sections and at the same time be able to maintain some of the zones closed of! or in non-producing condition until -a selected producing zone becomes exhausted; Thereafter it is desirable to ,be able to obtain production from one or the several other zones in a selected manner.

It is, therefore, an object of the invention to provide a method whereby a screen or perforate liner can be protected from danger during the setting operation.

Another object of the invention is to provide a method whereby fluid circulation can be posiparent as the description of the invention proceeds.

I have found that'by sealing the perforations in the perforate liner or screen with a suitable metal which is more readily and rapidly disintegrable or removable upon entering into a chemical reaction with a selected chemical solution than the metal comprising the conventional screen or liner or other metal well parts, a screen or perforate liner can be lowered into a well without'danger of being damaged or of the slots therein being clogged by mud, and at the same time fluid circulation can be positively established exteriorly of the liner so as to wash the mud or the like from the face of the producing formation and carry it from the well. The

readily removable metal sealing 'the perforations` of the desired mineral fluid vinto the well after the perforate liner has been positioned at the desired point. Further, if several producing zones are lined with perforate liners treated in the above manner, production can be selectively` obtained from each producing zone as desired.

In the accompanying drawings forming a Part of this specificationl Fig. 1 is a view in vertical cross section of an oil well bore showing a perforate liner covered lwith a chemically disintegrable or readily removable metal shell and positioned in the welladjacent the producing formation.

Fig. 2 is a, fragmentary view showing the Achemically removable metal covering partially disintegrated by the action of a suitable chemical solution so as to allow entrance of mineral fluid linto thewell through the liner perforations or slots.

Fig. 3 is an enlarged sectional view showing I the chemically removable metal covering. positioned interiorly of the screen or liner and in such a form that it fills the slots or perforations in said liner.

Fig. 4 is a view in vertical cross section showing a well bore penetrating several producing zones with perforate liners provided with chemically disintegrable or removable coverings incorporated in the conventional casing string.

^ As shown in Fig. 1 of the drawings, the upper portion I of the well is cased with conventional iron casing 2 to a point 3 where it is cemented in place by cement 4. The lower portion of the well bore 6 ends in a. productive stratum 5 from which oil flows into the well. The screen or perforate liner 1 provided with a chemically removable metal covering 8 is shown positioned in the Well adjacent the producing formation and extends substantially over the entire length thereof. The screen or liner 1, is sealed at its upper end to casing 2 as by packing means 9. A run-in string `I0 supports the liner 1 and serves'as a means whereby the liner is loweredr into the Well and positioned therein.' The lower end of the liner is provided with a 'cap member Il which screw-threadedly engages the liner and serves to hold the chemically removable metallic covering 8 in place. The cap II also serves as a housing for valve`|2 which is designed to allow fluid to flow out of the interior'- of the liner but prevents the flow of fluid into the interior, of the liner from the well bore. A

In the viewillustrated in Fig.y 2 the chemically removable metal covering 8 is lshown partially disintegrated, whereby fluid is enabled .to flow into the well through the slots in the liner.

`In Fig. 3 the disintegrable or chemically removable metallic covering I3 sealing the perforaof the liner and extends into the slots or perforations therein.

In the View shown in Fig. 4 the well bore passes through several productive zones designated by numerals I4, I5, and I 6, separated from each other by non-productive areas I1, I8, and I9. An iron casing or pipe 20 is shown lining the well bore and has incorporated therein at points adjacent the various productive zones perforate iron metal liner or screen sections 2I, 22, and 23. The perforate liner sectionsare attached to the metal casing by means of couplings or collars 24, 25,I 26, and 21, and are provided with chemically removable metal coverings in the form of cylindrical tubular metal shells 2,8, 29, and 30 which serve to maintain the perforations in a sealed condition thus excluding uid from entering the `well through the perforations. Eachv section of the ferrous metal casing 20 is shown sealed to the formation adjacent the non-productive areas by cement k3| which may be injected through suit able perforations 32, 33, yand 34 formed in the ferrous metal casing 20 adjacent each non-productive area. The introduction of the cement 3| may take place through the wel] tubing 35 s0 as to position the cement only adjacent the non-productiveA areas in the manner Well known in the art, such as bysqueezing the cement through the perforations 32 into the desired location while one portion of the Well bore is sealed from the other by a bridge, cement retainer, packer, 0r the like. The lower portion of the well bore interlorly of. the casing and. the perforate liner is shown filled with a chemical solution 36, which may be a, suitable acid selected for bringing about the-removal of the readily removable sections. The acid is retained within the casing by cap member 31 vthreadedly attached to the lower liner section.

In putting the invention in operation in the manner illustrated in Fig. 1 the perforate screen or linerlis covered with a tubular shell of a-metal more readily chemically removable than the metal liner. liner by screw cap II. The liner is then lowered into the well bore on the run-in string and positioned opposite the producing formation. The face of the producing formation may then be freed of mud and the like by a. washing operation wherein water or other solvent is forced out of the liner through the valve I I at a rate such that there will be a washing action on the face of the formation. Thereafter, the packing elementmay be seated so as to seal the liner to the well casing tions in the liner is shown positioned interiorlyy and the chemically removable shell disintegrated by means of a solution of a'. strong alkali or an acid so as to allow normal entry of the desired fluids through the perforate liner. y

In those instances where the Well lpenetrates i more than one productive stratum it will be desirable to use the combination illustrated in Fig.

4, wherein the casing string is made up of the desired number of perforate sections and in such a manner that when the well casing is positioned in the well bore the perforate sections, sealed with the chemically removable metal lining, will be positioned adjacent the several producing strata. The metallic casing 20 may then be ce mented in place so as to separate the several productive Astrata from each other. This may be readily accomplished by forcingthe 1 cement through the .special perforations 32., 33, and 34 formed in the metal casing 20 so as to yplace the cement only adjacent the non-productive areas. Such procedure is entirely conventional and well knownin the art. It usually consists in placing a bridge, cement retainer, packer orother sealing means in 'the casing-in such a manner as to separate the portion of the well bore to be sealed from the-remainder of the wellbore. Cement slurry is then squeezed into the annular space adjacent only the non-productive area;

Although the screen or other perforate member ordinarily used in practice is formed of ferrous metal, other materials may be satisfactorily used, such as bronze and similar metals not readily corrodible by well fluids and not readily attacked by the chemical solutions bringing about the removal of the sealing metal. Among the metals more readily chemically removable than the ordinarily used ferrous metal lineror other screen material suitable for sealing or coveringthe perforations are aluminum, zinc, and magnesium. The terms magnesium, aluminum, and zinc used herein and in the appended claims are intended to include these metals containing the ordinary impurities present in commercially pure metal as Well as alloys of these metals wherein such metals are the predominant constituent. As illustrated the perforations in the liner may be-sealed by employing one of the above metals in the form of a thin tubular shell which is preferably positioned exteriorly of the perforate member since the liner is better protected from damage, although if desired the seal maybe produced interiorly of the liner. The protective metal seal may take other forms, it being desirable rather than essential that the entire surface of the liner be covered. For example, it is only essential that the perforations be lled with the metal. The readily removable metal may be selected in The covering is secured in place on the accordance with the use to` which it is to be put. For example, when the chemically removable metal covering or sealing material is to be subjected to the action of the well fluids forfan extended period of time, such as when several producing sections are sealed off while producing from one zone, it will be found preferable to use either zinc or aluminum since these metals are more resistant to the well fluids.

Among the chemical solutions which will rapidly bring about disintegration of the readily removable metals above listed are acids such as hydrochloric and sulphuric as well as strongl bases such as sodium or potassium hydroxide,l the particular solution depending' upon specic metal or alloy employed. For example, aluminum is more readily attacked by strong alkaline solutions such as sodium and potassium hydroxide, but at the same time is soluble in acid solutions such as aqueous hydrochloric acid. On the other hand, magnesium and zinc will be found to be more readily disintegrated by the action -of an acid such as hydrochloric acid. If desired, in those cases where hydrochloric acid is employed for the removal step in the presence of iron and steel well parts, the acid may be inhibited against corrosive may vary quite widely. By way of illustration, the chemical in contact with the readily soluble removable metals from 2 to 6 hours or moreto bring about the desired disintegration.

In the foregoing manner a well may be completed in a single productive zone and a liner p0- sitioned therein without danger of damage to the liner and at the same time the formation face may be thoroughly cleansed of mud or other contaminating material. In addition, the ,well may be completed. in several productive zones and l each zone opened to production as desired by use of a chemical solution capable of bringing about disintegration of the sealing metal and l thus the flow of mineral fluid to the well.

attack upon iron or steel in the manner well known in the art whereby the sealing metal is readily andv rapidly removed Without' harmful effects to the iron or steel liner and well parts. The concentration of thel chemical solution effecting the removal may varyexample, concentrations of between 5 and 25-per cent may be satisfactorily employed. The amount of chemical solution to use may bereadily calculated from a knowledge of the amount of the quite widely. For

particular metal to be removed. The length of time required' for removal of the soluble metal This application is a continuation-impart of my cca-pending application Serial No. 247,270, filed December 22, 1938.

l. A well casing for completing a well penetrating a plurality of producing zones comprising' sections of ferrous metal pipe having Adisposedtherein sections of perforate ferrous metal pipe, said perforate sections being sealed against entry of fluid therethrough by a metal more readily chemically removable than the ferrous metal.

2. `A well casing according to claim-1 in which thev metal more readily chemically removable Vthan the ferrous metal is zinc.

3. A well casingvaccording to claim 1 in which the metal more readily chemically lremovable than the ferrous metal is aluminum.

4. A well casing according to claim l in which l the metal more readily chemically removable than the ferrous metal is magnesium.

EDWARD L. CARTER.

solution may be allowed to remain 

